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issue 21: parse floats in scientific notation #22

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Merged
robinheghan merged 1 commit into from
May 20, 2026
Merged

issue 21: parse floats in scientific notation #22

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58 changes: 50 additions & 8 deletions src/Compiler/Parse/Number.gren
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ import Compiler.Parse.Context exposing (Context)
-}
type Outcome
= Integer Int
| FloatingPoint Float
| FloatingPoint { val : Float, text : String }
| Hex Int


Expand Down Expand Up @@ -70,8 +70,8 @@ parser =
Integer int ->
Integer (negate int)

FloatingPoint float ->
FloatingPoint (negate float)
FloatingPoint record ->
FloatingPoint { record | val = negate record.val, text = "-" ++ record.text }

Hex hex ->
Hex (negate hex)
Expand Down Expand Up @@ -104,6 +104,7 @@ zeroOrHigher =
|> Parser.map Hex
, Parser.chompChar '.' NotANumber
|> Parser.andThen (\_ -> fractalParser "0")
, exponentParser "0"
, Parser.chompIf Char.isDigit NotANumber
|> Parser.andThen (\_ -> Parser.problem LeadingZero)
, Parser.succeed (Integer 0)
Expand All @@ -122,6 +123,7 @@ zeroOrHigher =
Parser.oneOf
[ Parser.chompChar '.' NotANumber
|> Parser.andThen (\_ -> fractalParser str)
, exponentParser str
, Parser.succeed (Integer num)
]
)
Expand All @@ -135,12 +137,52 @@ fractalParser str =
|> Parser.getChompedString
|> Parser.andThen
(\postDot ->
when String.toFloat (str ++ "." ++ postDot) is
Nothing ->
Parser.problem NotANumber
let
base = str ++ "." ++ postDot
in
Parser.oneOf
[ exponentParser base
, when String.toFloat base is
Nothing ->
Parser.problem NotANumber

Just float ->
Parser.succeed (FloatingPoint { val = float, text = base })
]
)

Just float ->
Parser.succeed (FloatingPoint float)

exponentParser : String -> Parser Context Error Outcome
exponentParser base =
Parser.chompIf (\c -> c == 'e' || c == 'E') NotANumber
|> Parser.getChompedString
|> Parser.andThen
(\eChar ->
Parser.oneOf
[ Parser.chompChar '+' NotANumber
|> Parser.getChompedString
, Parser.chompChar '-' NotANumber
|> Parser.getChompedString
, Parser.succeed ""
]
|> Parser.andThen
(\sign ->
Parser.chompIf Char.isDigit ExpectedInt
|> Parser.skip (Parser.chompWhile Char.isDigit)
|> Parser.getChompedString
|> Parser.andThen
(\expDigits ->
let
fullText = base ++ eChar ++ sign ++ expDigits
in
when String.toFloat fullText is
Nothing ->
Parser.problem NotANumber

Just float ->
Parser.succeed (FloatingPoint { val = float, text = fullText })
)
)
)

{-| A parser that only parses hex-encoded integers, like `0xAB`.
Expand Down
2 changes: 1 addition & 1 deletion tests/src/Test/Compiler/Parse/Expression.gren
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Expand Up @@ -29,7 +29,7 @@ tests =
)
, test "Float" <| \_ ->
Parser.run PE.parser Context.empty "3.14"
|> expectExpression (AST.NumberLiteral (Number.FloatingPoint 3.14))
|> expectExpression (AST.NumberLiteral (Number.FloatingPoint { val = 3.14, text = "3.14" }))
, test "Hex" <| \_ ->
Parser.run PE.parser Context.empty "0xDE"
|> expectExpression (AST.NumberLiteral (Number.Hex 0xDE))
Expand Down
35 changes: 32 additions & 3 deletions tests/src/Test/Compiler/Parse/Number.gren
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Expand Up @@ -34,20 +34,49 @@ tests =
|> Result.map
(\outcome ->
when outcome is
PN.Integer value ->
PN.FloatingPoint (toFloat value)
PN.Integer value ->
PN.FloatingPoint { val = toFloat value, text = String.fromInt value }

_ ->
outcome
)
|> Expect.equal (Ok (PN.FloatingPoint float))
|> Expect.equal (Ok (PN.FloatingPoint { val = float, text = String.fromFloat float }))
, test "Requires a number after ." <| \{} ->
run "0."
|> expectErr PN.ExpectedInt
, test "when followed by letter, it fails" <| \{} ->
run "0.15a"
|> expectErr PN.NotANumber
]
, describe "Scientific notation"
[ test "integer with exponent" <| \{} ->
run "1e5"
|> Expect.equal (Ok (PN.FloatingPoint { val = 1.0e5, text = "1e5" }))
, test "zero with exponent" <| \{} ->
run "0e3"
|> Expect.equal (Ok (PN.FloatingPoint { val = 0.0e3, text = "0e3" }))
, test "decimal with exponent" <| \{} ->
run "1.5e3"
|> Expect.equal (Ok (PN.FloatingPoint { val = 1.5e3, text = "1.5e3" }))
, test "uppercase E" <| \{} ->
run "1.5E3"
|> Expect.equal (Ok (PN.FloatingPoint { val = 1.5e3, text = "1.5E3" }))
, test "explicit positive exponent" <| \{} ->
run "1.5e+3"
|> Expect.equal (Ok (PN.FloatingPoint { val = 1.5e3, text = "1.5e+3" }))
, test "negative exponent" <| \{} ->
run "1.5e-3"
|> Expect.equal (Ok (PN.FloatingPoint { val = 1.5e-3, text = "1.5e-3" }))
, test "negative number with exponent" <| \{} ->
run "-1.5e3"
|> Expect.equal (Ok (PN.FloatingPoint { val = -1.5e3, text = "-1.5e3" }))
, test "requires digits after e" <| \{} ->
run "1e"
|> expectErr PN.ExpectedInt
, test "requires digits after e sign" <| \{} ->
run "1e+"
|> expectErr PN.ExpectedInt
]
, describe "Hex"
[ test "Can parse hex" <| \{} ->
run "0xAFFE"
Expand Down
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